DFM cryogenic features

DFX cryogenic features

Preliminary design of the electrical feeding devices for the HL LHC superconducting powering

W.Bailey2, A.Ballarino1, R.Betemps1, I.Falorio1, Y.Leclercq1, V.Parma1, F.Pasdeloup1, Y.Yang2

CERN, Geneva, Switzerland1, University of Southampton, United Kingdom2

Abstract. The High Luminosity LHC (HL-LHC) project aims at upgrading the LHC collider after 2025 to increase its luminosity by about a factor of five. As part of this upgrade, new magnets will require an electrical powering system where the power converters are placed in a newly dug service gallery to shield

them from the radiations emanating from the colliding beams. The electrical powering will be ensured via a superconducting line, in MgB2, housed into a flexible cryostat of length up to 140 meters, and carrying currents along diverse circuits between 0.6 kA and 18 kA. At the extremities of the flexible cryostats,

electrical interconnection devices allow connecting the superconducting cables to the magnets in the LHC tunnel and to the current leads and power converters in the service galleries. Moreover, the devices ensure a regulated cooling by a vapour mass flow of helium through the continuous powering chain up to 10

g.s-1, at about 1.3 bar, and in the 4.5-17 K temperature range. This paper presents the technical requirements and the preliminary design of the electrical interconnection devices. The operating modes during transient and nominal phases are presented as well as the thermo-mechanical and cryogenic flow layouts.

Integration and assembly in the LHC machine are also explained, including specific safety aspects and maintainability requirements.

Context & Cold Powering System principle The High Luminosity LHC project requires the installation of new magnets focusing the beam on each

side of the 2 interaction points (ATLAS and CMS). The resultant higher levels of radiation require the

electronics to be installed in newly dug parallel galleries to provide sufficient shielding and allow access

for intervention.

To connect the magnets to the power converters, each side of the interaction point presents two cold

powering systems made of:

A superconducting link (DSHx or DSHm) carrying up to 19 MgB2 cables over 100 to 140 m

A connection box to the magnets (DFX or DFM)

A connection box to the current leads (DFHx or DFHm)

, being studied. DFM basic functions:

Electrical interface SCLink & matching section

Ensure operating temperature of SC cables

Supply 4.5 K GHe mass flow to DSHm

Key concepts:

SCLink connects to the DFM angularly

“Fountain” design with two LHe volumes ensures

permanent immersion of splices & NbTi leads

The DFM heater is controlled by the DFHm needs

The liquid level monitoring controls the inlet valve

MgB

2 -Nb

Ti splice

s

LHe inlet

Nominal level

Λ plate

LHe inlet

Nominal level

Λ platePrinciple:LHe is injected in the mainvolume, submerges splices andoverflows in a side reservoirwhere it is vaporised to create aGhe mass flow routed back tothe SCLink inner volume.

Nominal level

A-ASection view

Courtesy A.KolehmainenDFM cryogenic concept in nominal configuration

DFX basic functions:

Electrical interface SCLink & triplet magnets

Ensure operating temperature of SC cables

Supply 4.5 K GHe mass flow to DSHx

Warm cables connect the Power converters to the current leads300K side. HTS cables connect the current leads to the MgB2

cables in the DFH. In the DFX, the MgB2 leads present NbTiextensions, connected to the λ plate’s leads.

Cold Powering System principle

Table 1. Temperature requirements for electrical leads and connections in

operation.

ItemNbTi

lead

MgB2

lead

HTS

lead

NbTi-NbTi

connection

MgB2-NbTi

connection

MgB2-HTS

connection

Maximum

Temperature[K] 5.5 17 50 5.5 5.5 17

Table 2. Helium mass flow through the cold

powering chain of cryostats.

Section Nominal

[g.s-1]

Design

[g.s-1]

Triplet 5 10

Matching 2 3

The cryogenic layout and operation modes shall ensure maximum temperatures of the cables and electrical connections as well as continuous mass flows

C2Po2C-04 [06]

Principle:LHe is injected in the lower volume,submerges splices and overflows inouter volume where it is vaporisedto create a Ghe mass flow throughthe SCLink.

Key concepts:

SCLink connects to the DFX vertically

“Fountain” design with two LHe volumes ensures

permanent immersion of splices & NbTi leads

The DFX heater is controlled by the DFHx needs

The liquid level monitoring controls the inlet valve

DFX cryogenic concept in nominal configuration

3D illustrative view

NbTi leads NbTi-NbTisplice

Heater

Safety pressure relief deviceSC Link

SC Link NbTi-NbTisplice

Heater

Safety pressure relief device

NbTi leads

Vaporisation volume

Cables volume

Level gauge

Level gauge